1. Field of Invention
The invention relates to water blast systems of the type using a small volume, high pressure, water jet typically in the range of up to about 10,000 psi and a water volume of about 4 to 6 gallons per minute, the jet being formed by passing the high pressure water through a small opening which may be round for forming a straight water jet or slotted for forming a fan jet.
2. Description of Prior Art
Water blast systems of the character described have in recent years become widely used for cutting, stripping and cleansing operations such as removal of paint, corrosion, rust, scale as required in preparation for painting or for boiler coil cleaning and the like; cutting of green concrete; stripping marine growth and oxidized paint from ships' hulls; removing polymers from heat exchangers and residues from evaporating tubes in chemical plants; and etc. The water blast system may be used in many instances in place of dry sand blasting or sand or other abrasive material may be introduced into the water jet.
Water blast systems customarily use a high pressure positive displacement pump driven by an internal combustion engine or electric motor, the pump being connected by a high pressure hose to a manually directed nozzle usually some distance away from the pump and engine. Some form of remote control system is required for the operator, at the nozzle, to control the operation of the power source, i.e., the rpm of the pump drive. Such remote controlled operation has certain disadvantages. It is normally possible to operate only one nozzle from one fluid pressure source since the source must be at all times under the control of an individual operator to meet his individual demands. Also there is danger of failure of the control caused by shorting or open circuit in an electric line or by bending or kinking of a pneumatic or hydraulic control hose, any of which may cause an increase in the pump output and correspondingly an increase in line pressure without prior notice to the operator.
The foregoing controls also involve a certain time delay, usually several seconds from the time of shutoff at the nozzle to actual significant reduction in pressure. The control systems are inherently cumbersome and bulky in the requirement of the additional cables, conduits and the like, as well as the switches, valves and other controls connected thereto.